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http://hdl.handle.net/20.500.12386/26271
Titolo: | The discovery, monitoring and environment of SGR J1935+2154 | Autori: | ISRAEL, Gian Luca Esposito, P. Rea, N. Coti Zelati, F. Tiengo, A. CAMPANA, Sergio MEREGHETTI, Sandro RODRIGUEZ CASTILLO, Guillermo Andres Götz, D. BURGAY, MARTA POSSENTI, ANDREA Zane, S. Turolla, R. Perna, R. Cannizzaro, G. Pons, J. |
Data pubblicazione: | 2016 | Rivista: | MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY | Numero: | 457 | Fascicolo: | 4 | Da pagina:: | 3448 | Abstract: | We report on the discovery of a new member of the magnetar class, SGR J1935+2154, and on its timing and spectral properties measured by an extensive observational campaign carried out between 2014 July and 2015 March with Chandra and XMM-Newton (11 pointings). We discovered the spin period of SGR J1935+2154 through the detection of coherent pulsations at a period of about 3.24 s. The magnetar is slowing down at a rate of Pdot = 1.43(1)× 10^{-11} s/s and with a decreasing trend due to a negative ddot{P} of -3.5(7) × 10^-19 s/s^-2. This implies a surface dipolar magnetic field strength of ∼2.2 × 10^14 G, a characteristic age of about 3.6 kyr and a spin-down luminosity L_sd ∼1.7 × 10^34 erg/s. The source spectrum is well modelled by a blackbody with temperature of about 500 eV plus a power-law component with photon index of about 2. The source showed a moderate long-term variability, with a flux decay of about 25 per cent during the first four months since its discovery, and a re-brightening of the same amount during the second four months. The X-ray data were also used to study the source environment. In particular, we discovered a diffuse emission extending on spatial scales from about 1 arcsec up to at least 1 arcmin around SGR J1935+2154 both in Chandra and XMM-Newton data. This component is constant in flux (at least within uncertainties) and its spectrum is well modelled by a power-law spectrum steeper than that of the pulsar. Though a scattering halo origin seems to be more probable we cannot exclude that part, or all, of the diffuse emission is due to a pulsar wind nebula. | Acknowledgments: | The scientific results reported in this article are based on observations obtained with the Chandra X-ray Observatory and XMM–Newton, an ESA science mission with instruments and contributions directly funded by ESA Member States and NASA. This research has made use of software provided by the Chandra X-ray Center (CXC) in the application package CIAO, and of softwares and tools provided by the High Energy Astrophysics Science Archive Research Center (HEASARC), which is a service of the Astrophysics Science Division at NASA/GSFC and the High Energy Astrophysics Division of the Smithsonian Astrophysical Observatory. This research is based on observations with the NASA/UK/ASI Swift mission. We thank N. Schartel for approving the XMM–Newton 2014 November observation through the Director's Discretionary Time program and the staff of the XMM–Newton Science Operation Center for performing the Target of Opportunity observations. Similarly, we thank B. Wilkes for approving the Chandra 2014 August observation through the Director's Discretionary Time program and the Chandra staff for performing the Target of Opportunity observations. We thank the Swift duty scientists and science planners for making these observations possible. The Parkes radio telescope is part of the Australia Telescope which is funded by the Commonwealth of Australia for operation as a National Facility managed by CSIRO. The authors warmly thank Phil Edwards for the prompt scheduling of the observations and John Reynolds for releasing part of the telescope time of his project. We thanks Jules Halpern for useful comments. NR is supported by an NWO Vidi Grant, and by grants AYA2012-39303 and SGR2014-1073. This work is partially supported by the European COST Action MP1304 (NewCOMPSTAR). | URI: | http://hdl.handle.net/20.500.12386/26271 | URL: | https://academic.oup.com/mnras/article/457/4/3448/2588925 | ISSN: | 0035-8711 | DOI: | 10.1093/mnras/stw008 | Bibcode ADS: | 2016MNRAS.457.3448I | Fulltext: | open |
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